package com.zrpc.core;

/**
 * 用于全局id生成
 * */
public class IdWorker {

	private final long workerId;
	private final static long twepoch = 1361753741828L;
	private long sequence = 0L;
	private final static long workerIdBits = 4L;
	public final static long maxWorkerId = -1L ^ -1L << workerIdBits;
	private final static long sequenceBits = 10L;
	private final static long workerIdShift = sequenceBits;
	private final static long timestampLeftShift = sequenceBits + workerIdBits;
	public final static long sequenceMask = -1L ^ -1L << sequenceBits;
	private long lastTimestamp = -1L;

	public IdWorker(final long workerId) {
		if (workerId > maxWorkerId || workerId < 0) {
			throw new IllegalArgumentException(String.format(
			"worker Id can't be greater than %d or less than 0",maxWorkerId));
		}
		this.workerId = workerId;
	}

	public synchronized long nextId() {
		long timestamp = this.timeGen();
		if (this.lastTimestamp == timestamp) {
			this.sequence = (this.sequence + 1) & sequenceMask;
			if (this.sequence == 0) {
				System.out.println("###########" + sequenceMask);
				timestamp = this.tilNextMillis(this.lastTimestamp);
			}

		} else {
			this.sequence = 0;
		}

		if (timestamp < this.lastTimestamp) {
			try {
				throw new Exception(
				String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds",
				this.lastTimestamp - timestamp));

			} catch (Exception e) {
				e.printStackTrace();
			}

		}

		this.lastTimestamp = timestamp;

		long nextId = ((timestamp - twepoch << timestampLeftShift))

		| (this.workerId <<workerIdShift) | (this.sequence);

//		 System.out.println("timestamp:" + timestamp + ",timestampLeftShift:"
//		 + timestampLeftShift + ",nextId:" + nextId + ",workerId:"
//		 + workerId + ",sequence:" + sequence);

		return nextId;

	}

	private long tilNextMillis(final long lastTimestamp) {

		long timestamp = this.timeGen();
		while (timestamp <= lastTimestamp) {
			timestamp = this.timeGen();
		}

		return timestamp;

	}

	private long timeGen() {
		return System.currentTimeMillis();
	}

	public static void main(String[] args) {

		IdWorker worker2 = new IdWorker(2);

		System.out.println(worker2.nextId());
		System.out.println(worker2.nextId());

	}

}
